diff --git a/google/api_core/retry.py b/google/api_core/retry.py
index 6198bfd1..98b8bbd9 100644
--- a/google/api_core/retry.py
+++ b/google/api_core/retry.py
@@ -93,19 +93,23 @@ class RetryFailureReason(Enum):
     """
     The cause of a failed retry, used when building exceptions
     """
+
     TIMEOUT = "TIMEOUT"
     NON_RETRYABLE_ERROR = "NON_RETRYABLE_ERROR"
 
 
 def _build_retry_error(
-    exc_list: list[Exception], reason: RetryFailureReason, timeout_val: float, **kwargs: Any
+    exc_list: list[Exception],
+    reason: RetryFailureReason,
+    timeout_val: float,
+    **kwargs: Any,
 ) -> tuple[Exception, Exception | None]:
     """
     Default exception_factory implementation. Builds an exception after the retry fails
 
     Args:
       - exc_list (list[Exception]): list of exceptions that occurred during the retry
-      - reason (google.api_core.retry.RetryFailureReason): reason for the retry failure. 
+      - reason (google.api_core.retry.RetryFailureReason): reason for the retry failure.
             Can be TIMEOUT or NON_RETRYABLE_ERROR
       - timeout_val (float): the original timeout value for the retry, for use in the exception message
 
diff --git a/google/api_core/retry_streaming.py b/google/api_core/retry_streaming.py
index bd93d235..114b47fd 100644
--- a/google/api_core/retry_streaming.py
+++ b/google/api_core/retry_streaming.py
@@ -94,7 +94,9 @@ def retry_target_stream(
     timeout = kwargs.get("deadline", timeout)
     deadline: Optional[float] = time.monotonic() + timeout if timeout else None
     error_list: List[Exception] = []
-    exc_factory = partial(exception_factory or retries._build_retry_error, timeout_val=timeout)
+    exc_factory = partial(
+        exception_factory or retries._build_retry_error, timeout_val=timeout
+    )
 
     for sleep in sleep_generator:
         # Start a new retry loop
@@ -109,14 +111,17 @@ def retry_target_stream(
             error_list.append(exc)
             if not predicate(exc):
                 final_exc, source_exc = exc_factory(
-                    exc_list=error_list, reason=retries.RetryFailureReason.NON_RETRYABLE_ERROR
+                    exc_list=error_list,
+                    reason=retries.RetryFailureReason.NON_RETRYABLE_ERROR,
                 )
                 raise final_exc from source_exc
             if on_error is not None:
                 on_error(exc)
 
         if deadline is not None and time.monotonic() + sleep > deadline:
-            final_exc, source_exc = exc_factory(exc_list=error_list, reason=retries.RetryFailureReason.TIMEOUT)
+            final_exc, source_exc = exc_factory(
+                exc_list=error_list, reason=retries.RetryFailureReason.TIMEOUT
+            )
             raise final_exc from source_exc
         _LOGGER.debug(
             "Retrying due to {}, sleeping {:.1f}s ...".format(error_list[-1], sleep)
diff --git a/google/api_core/retry_streaming_async.py b/google/api_core/retry_streaming_async.py
index 96c03aec..cd733e1c 100644
--- a/google/api_core/retry_streaming_async.py
+++ b/google/api_core/retry_streaming_async.py
@@ -165,7 +165,9 @@ async def retry_target_stream(
         except (Exception, asyncio.CancelledError) as exc:
             error_list.append(exc)
             if not predicate(exc):
-                exc, source_exc = exc_factory(exc_list=error_list, reason=RetryFailureReason.NON_RETRYABLE_ERROR)
+                exc, source_exc = exc_factory(
+                    exc_list=error_list, reason=RetryFailureReason.NON_RETRYABLE_ERROR
+                )
                 raise exc from source_exc
             if on_error is not None:
                 on_error(exc)
@@ -175,7 +177,9 @@ async def retry_target_stream(
 
         # sleep and adjust timeout budget
         if deadline is not None and time.monotonic() + sleep > deadline:
-            final_exc, source_exc = exc_factory(exc_list=error_list, reason=RetryFailureReason.TIMEOUT)
+            final_exc, source_exc = exc_factory(
+                exc_list=error_list, reason=RetryFailureReason.TIMEOUT
+            )
             raise final_exc from source_exc
         _LOGGER.debug(
             "Retrying due to {}, sleeping {:.1f}s ...".format(error_list[-1], sleep)